Middle three digits

Middle three digits is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

The task is to:

“Write a function/procedure/subroutine that is called with an integer value and returns the middle three digits of the integer if possible or a clear indication of an error if this is not possible.”

Your function should be tested with the following values; the first line should return valid answers, those of the second line should return clear indications of an error:

123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345
1, 2, -1, -10, 2002, -2002, 0

Show your output on this page.

D

Translation of: Python

<lang d>import std.stdio, std.traits, std.math, std.conv;

string middleThreeDigits(T)(T n) if (isIntegral!T) {

   auto s = n.abs().text();
   auto len = s.length;
   if (len < 3 || len % 2 == 0)
       throw new Exception("Need odd and >= 3 digits");
   auto mid = len / 2;
   return s[mid - 1 .. mid + 2];

}

void main() {

   auto passing = [123, 12345, 1234567, 987654321, 10001, -10001,
           -123, -100, 100, -12345];
   auto failing = [1, 2, -1, -10, 2002, -2002, 0];
   foreach (n; passing ~ failing) {
       string answer;
       try {
           answer = middleThreeDigits(n);
       } catch (Exception e) {
           answer = e.msg;
       }
       writefln("middleThreeDigits(%s) returned: %s", n, answer);
   }

}</lang>

middleThreeDigits(123) returned: 123
middleThreeDigits(12345) returned: 234
middleThreeDigits(1234567) returned: 345
middleThreeDigits(987654321) returned: 654
middleThreeDigits(10001) returned: 000
middleThreeDigits(-10001) returned: 000
middleThreeDigits(-123) returned: 123
middleThreeDigits(-100) returned: 100
middleThreeDigits(100) returned: 100
middleThreeDigits(-12345) returned: 234
middleThreeDigits(1) returned: Need odd and >= 3 digits
middleThreeDigits(2) returned: Need odd and >= 3 digits
middleThreeDigits(-1) returned: Need odd and >= 3 digits
middleThreeDigits(-10) returned: Need odd and >= 3 digits
middleThreeDigits(2002) returned: Need odd and >= 3 digits
middleThreeDigits(-2002) returned: Need odd and >= 3 digits
middleThreeDigits(0) returned: Need odd and >= 3 digits

Python

<lang python>>>> def middle_three_digits(i): s = str(abs(i)) length = len(s) assert length >= 3 and length % 2 == 1, "Need odd and >= 3 digits" mid = length // 2 return s[mid-1:mid+2]

>>> passing = [123, 12345, 1234567, 987654321, 10001, -10001, -123, -100, 100, -12345] >>> failing = [1, 2, -1, -10, 2002, -2002, 0] >>> for x in passing + failing: try: answer = middle_three_digits(x) except AssertionError as error: answer = error print("middle_three_digits(%s) returned: %r" % (x, answer))

middle_three_digits(123) returned: '123' middle_three_digits(12345) returned: '234' middle_three_digits(1234567) returned: '345' middle_three_digits(987654321) returned: '654' middle_three_digits(10001) returned: '000' middle_three_digits(-10001) returned: '000' middle_three_digits(-123) returned: '123' middle_three_digits(-100) returned: '100' middle_three_digits(100) returned: '100' middle_three_digits(-12345) returned: '234' middle_three_digits(1) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(2) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(-1) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(-10) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(2002) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(-2002) returned: AssertionError('Need odd and >= 3 digits',) middle_three_digits(0) returned: AssertionError('Need odd and >= 3 digits',) >>> </lang>